look up any word, like the eiffel tower:
 
1.
Where one person eats a bunch of bananas and chases it with ex-lax. Then you dress as a monkey then proceed to take a massive fountain-like dump on your partners back.
Last night was amazing til you bananabacked me in my sleep!
by Sprint monkey shart February 13, 2010
 
2.
The arch in some chick's backs when standing, showing off their ass. The chick's back curves like a Banana, making her ass appear to be more pronounced than without a Banana Back.
A: Hey, Katie has a nice Banana Back! I could stare at that all day!

B: Yeah, I know! that ass is seductive!
by kikr47 November 20, 2008